49ers' Kyle Williams done for season

Williams announced via Twitter on Monday that he sustained a season-ending left knee injury against the New Orleans Saints.

"Regret to inform y'all I will be out for the season with a torn ACL," he wrote. "Not how I saw things playing out, but in the end I will be fine."

Williams crumpled to the ground after a 2-yard run by Kendall Hunter near the end of the third quarter.

On that same play, Hunter also suffered a potentially serious ankle injury.

Coach Jim Harbaugh declined to get into specific injuries Monday, saying that players were still being evaluated, but he acknowledged the possibility that the 49ers' top two draft picks might finally hit the field.

Receiver A.J. Jenkins (first-round pick) and running back LaMichael James (second round) have yet to play this season.

Asked about the outlook for Jenkins and James, Harbaugh said: "There's a good chance there'll be some new active guys on Sunday. ... To both those youngsters' credit, and others who have been working extremely hard for their opportunity, we feel good and excited that a couple of those youngsters will get that opportunity."

Williams, 24, led the 49ers this season with a 27.2-yard average on his 13 kickoff returns. As the team's No. 3 receiver, he also had 14 catches for 212 yards.

On Twitter, Williams thanked fans for their outpouring of support

"This is just another obstacle. I will have to climb back," he wrote. "Love all true fans. Your prayers are much appreciated."

* With Williams poised to go on injured reserve, the 49ers could sign another player. Former Eagles receiver/returner Chad Hall is a possibility, according to Adam Caplan, an analyst for philadelphiaeagles.com. Kaplan reported that the 49ers have interest in the 26-year-old former Air Force standout, and Hall later tweeted, "California, California, hear we cooooooome."

* There no update on tight end Delanie Walker, who left Sunday's game with a hip injury. "We'll see," Harbaugh said. "We haven't got the final report. It was a hard-hitting game. It took a toll."

Walker walked out of the locker room after the game but was then placed on a cart that took him to the team bus.

* Aldon Smith moved within six sacks of Michael Strahan's single-season NFL record (22??1/2 in 2001). "Proud as heck for Aldon," Harbaugh said. "Let's keep on truckin'."

* Among the things that most pleased Harbaugh about Sunday's defensive effort was the 49ers' sure tackling. He suspected there might have been only one missed tackle but wanted to watch the game film to make sure. Harbaugh said preventing yards after the catch was a huge factor against the Saints, especially against backfield dynamo Darren Sproles.

* The 49ers-Saints game will be featured on the NFL Network's "NFL Replay" show Tuesday at 6:30 p.m.?? The show condenses the action to 90 minutes and uses bonus footage from NFL Films and NFL Network coverage.

* The 49ers did not allow a sack on any of Colin Kaepernick's 25 pass attempts. It is the second time this season the offensive line allowed no sacks. (Also Oct. 7 vs. Buffalo.)